This invention is generally for use in the drilling of boreholes and is specifically suited for the drilling of boreholes and piling foundation holes in cold regions such as Alaska and Canada.
In the past, the apparatus utilized to seal between the drill pipe and the borehole wall when drilling boreholes or pile foundation holes involved the use of a flat plate with a hole therethrough. The flat plate is slipped over the drill pipe and pressed against the ground over the borehole annulus.
This suffers from the disadvantage of a poor seal against both the ground and the drill pipe, especially when the ground is rough or uneven, frozen, or rocky. Also the seal against the drill pipe is poor since the plate must give the pipe room to flex and move slightly to prevent wear between the pipe and the plate.
The present invention overcomes these disadvantages by providing a drilling head which is flexible enough to conform to the borehole profile and allow the drill pipe movement yet still provide a good seal.